Lesser Ring of the Lycanthrope (5e Equipment)

From D&D Wiki

A magic ring hastily put together by a spellcaster to prevent lycanthropes from hurting the innocent. While it does allow the wearer to retain their mental composure, their physical changes will occur much more frequently and with painful side effects. Upon close inspection, one will notice that the ring is made of a hardened plant material. A shimmering blue gem that holds the magical properties of the ring sits in its center.

Calmed Nerves. You gain advantage on Wisdom saving throws you make due to the "Bloodlust" and "Emotionally Unstable" rules. In addition, if you transform under the full moon, you can make a DC 25 Wisdom saving throw. On a successful save, control of your character isn't given to the DM. You still revert to your humanoid form when the sun rises.

Curse. Because the ring heightens the humanity of the wearer, the ring has a detrimental side-effect. While you are in your hybrid or animal form, you must make a DC 15 Constitution saving throw or take 2d4 necrotic damage, or half as much damage on a successful save. You must make this saving throw every hour if you are not in combat, or at the start of each of your turns if you are in combat. This curse can be removed from the wearer with the remove curse spell, but the curse will remain on the ring.